Many home gardeners and farmers experiment
as often as scientists do. But as valuable as the gardeners' and farmers'
experiments are, their results are usually called "folklore,"
not science.

They often want scientists to test their
folklore, to see if it really works. That's what happened
with organic farmers and gardeners who discovered
that common household vinegar kills weeds.

They started using vinegar instead of
chemical weed killers and recommend it to friends. Not all of them were
entirely convinced, though, and some had questions that the scientists
could best answer. Like, would vinegar ruin the soil because it is such
a strong acid?

Three Agricultural Research Service (ARS)
weed scientists in Beltsville, Maryland--Jay Radhakrishnan, John Teasdale
and Ben Coffman--decided to do scientific experiments to find out.

They knew that if it worked, vinegar would
be great for farmers and gardeners who choose not to use most weed-killing
chemicals, called herbicides.

They tested vinegar on five major weeds.
One of these was Canadian thistle. You may have noticed it growing in
your own backyard, around walls, the patio or on the side of the road.

In a greenhouse, the three scientists
hand-sprayed the thistle with different solutions of vinegar. Typical
white vinegar bought from the store was the weakest mixture--95 percent
water and about 5 percent vinegar.

In tests, though, this solution was enough
to kill Canadian thistle, giant foxtail, smooth pigweed and two other
weeds up to 2 weeks old. The vinegar caused the young weeds' leaves to
shrivel up, turn brown and die. But older plants needed stronger vinegar
solutions to finish them off. For example, against older Canadian thistles,
the scientists found they had to drench the pesky plants' roots in order
to totally kill them. Just spraying the leaves didn't quite do the trick.

The scientists also did a little testing
on cornfields. They found they could kill most--or all--of the weeds there
without harming the corn. Their tests also showed that vinegar only makes
the soil slightly more acidic, and only for a few days.

The weed scientists are glad the farmers
and gardeners discovered vinegar as an organic weed killer. And the farmers
and gardeners are happy to receive scientific information about how to
use it best.

"Usually scientists are the first
to discover things like chemicals that kill weeds," said Dr. Teasdale,
one of the three ARS researchers. "But this time, it was the opposite
of the way it usually works. The farmers and gardeners discovered this
natural weed killer. We scientists came in toward the end, with proof
about how effective and safe it is."